The present invention relates to an optical shutter structure and more particularly diffuse a reflecting optical shutter structure. Optical shutters are a layer or layers which have variable light transmission.
Optical shutters may be a layer or layers covering an aperture. The shutter may be reversibly activated by: (1) its local temperature (thermochromic); (2) incident light intensity (photochromic); (3) both temperature and light (thermophotochromic); or (4) an electric current or field (electrochromic). The combination of transparent insulations with a layer of thermochromic optical shutter is the subject of U.S. Pat. Nos. 4,085,999 and 3,953,110 by the applicant herein. Thermochromic and thermophotochromic shutters, not in combination with a transparent insulation, are the subject of U.S. Pat. No. 4,307,942 and U.S. patent application Ser. No. 06/948,039 ("'039 application") by the applicant herein entitled "Structure and Preparation of Automatic Light Valves," filed on Dec. 31, 1986. Further, my U.S. Pat. No. 4,307,942 and my '039 patent application describes "cloud gel", which reflects through inhomogeneous dielectrics. See also, "Thinking Window switches Off the Sun When it is Hot", Popular Science, March, 1984, and my article "Contractor Designed Passive Heating, Cooling, and Daylighting", U.S. Passive Solar Conference (March 1990).
To best understand the invention, reference is made to the Encyclopedia of Science & Technology, Second Edition, McGraw Hill (1989) for a general definition of terms. Specifically, reference is made to Large Area Chromogenics, edited by C. M. Lampert, SPIE Optical Engineering Press (1988); Optical Materials Technology of Energy, Efficiency and Solar Energy Conversion, edited by C. G. Granqvist, Vol. 9 (1990), Vol. 8 (1989), Vol. 7 (1988); Material & Optics for Solar Energy Conversion and Advanced Lighting Technology, edited by C. M. Lampert, SPIE Optical Engineering Press (1986). These publications set forth a comprehensive overview of technology related to this invention.
The reflectance of some optical shutters is primarily specular. Specular reflectance is objectionable in some applications; for example, domestic windows where people do not want to see their reflections mirrored in the windows from either inside or outside the home.
This problem can be overcome by forming the the optical shutter element of the optical shutter structure on or onto a layer with an optically rough surface, and then forming another layer on or onto the optical shutter whose refractive index approximately matches that of the layer with a rough surface, and whose surface not contiguous with the shutter is smooth, as shown in FIGS. 1 and 2.
None of the patents and patent applications described above provides the important advantage of transmitting light specularly but reflecting it diffusely. In other words a person looking through this improved shutter optical would see through it clearly whether the shutter optical were in its transmissive or reflective mode, but this person would not see any clear reflections in the shutter in either mode. The specular transmission of light is accomplished by forming the optical shutter element of the optical shutter structure on or onto a layer with a rough surface, and then forming another layer on or onto the shutter whose refractive index approximately matches that of the layer with a rough surface, and whose surface not contiguous with the shutter is smooth. In this manner, objectionable specular reflectance is eliminated.